The images of Saints Cyril and Methodius, known as the 'Thessaloniki brothers', creators of the Glagolitic alphabet, during the perception of the Old-Bulgarian language as a Church language and script, for translation of liturgical books from Greek into Slavonic. The Glagolitic alphabet was created in 855 on the base of Bulgarian runic script (lines and dashes), with adding the three symbols of Christianity, cross, circle and triangle depicting the unity of the Trinity.